freebsd-dev/sys/boot/arm/uboot/start.S

/*-
 * Copyright (c) 2008 Semihalf, Rafal Czubak
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD$
 */

#include <machine/asm.h>
#include <machine/armreg.h>

/*
 * Entry point to the loader that U-Boot passes control to.
 */
	.text
	.globl	_start
_start:
	/* Hint where to look for the API signature */
	ldr	ip, =uboot_address
	str	sp, [ip]

	/* Save U-Boot's r8 and r9 */
	ldr	ip, =saved_regs
	str	r8, [ip, #0]
	str	r9, [ip, #4]

#ifdef _ARM_ARCH_6
	mrc     p15, 0, r2, c1, c0, 0
	orr	r2, r2, #(CPU_CONTROL_UNAL_ENABLE)
	orr	r2, r2, #(CPU_CONTROL_AFLT_ENABLE)
	mcr     p15, 0, r2, c1, c0, 0
#endif

	/* Start loader */
	b	main

/*
 * syscall()
 */
ENTRY(syscall)
	/* Save caller's lr, r8 and r9 */
	ldr	ip, =saved_regs
	str	r8, [ip, #8]
	str	r9, [ip, #12]
	str	lr, [ip, #16]
	/* Restore U-Boot's r8 and r9 */
	ldr	r8, [ip, #0]
	ldr	r9, [ip, #4]
	/* Call into U-Boot */
	ldr	lr, =return_from_syscall
	ldr	ip, =syscall_ptr
	ldr	pc, [ip]
return_from_syscall:
	/* Restore loader's r8, r9 and lr */
	ldr	ip, =saved_regs
	ldr	lr, [ip, #16]
	ldr	r9, [ip, #12]
	ldr	r8, [ip, #8]
	/* Return to caller */
	mov	pc, lr

/*
 * Data section
 */
	.data
	.align	4
	.globl	syscall_ptr
syscall_ptr:
	.long	0

	.globl	uboot_address
uboot_address:
	.long	0

saved_regs:
	.long	0	/* U-Boot's r8 */
	.long	0	/* U-Boot's r9 */
	.long	0	/* Loader's r8 */
	.long	0	/* Loader's r9 */
	.long	0	/* Loader's lr */